Template constraints should introduce identifiers inside their scopes

[Nick Treleaven]

On Wednesday, 21 September 2022 at 11:23:57 UTC, HuskyNator wrote:
> Consider these semantically identical functions:
>
> ```d
> void bar(M)(M list) if (is(M : T[L], T, uint L)) {
> 	pragma(msg, "Length: " ~ L.to!string); // undefined identifier 
> 'L'
> }
> ```

This is in bugzilla:
https://issues.dlang.org/show_bug.cgi?id=6269